Parallel vector memories in the brain of a bee as foundation for flexible navigation

Significance Insects navigate by utilizing path integration (vector-based navigation) and landmark guidance for homing. Bees also exhibit more complex behaviors, including creating novel shortcuts between locations. Though novel shortcuts have historically been indicative of a cognitive map, its existence in insects is highly contentious. Investigating condensed foraging behaviors in walking bumblebees, we reveal that multiple vectors learned during path integration can be transferred to parallel long-term memories and that these vectors can be recalled at a familiar location for homeward navigation—both fundamental requirements of a vector-based mental map. Our demonstration of the flexible use of long-term navigation vectors provides a plausible foundation for how bees achieve vertebrate-like, high-level navigation behaviors with far fewer neurons in their brains.

Note that hive five had very few individuals who oriented as predicted from a recalled long-term vector memory.Limited foraging trips during the training period may explain why some individuals initially oriented as predicted from a path integration vector constructed in working memory rather than a long-term vector memory.Sens Neural Behav Physiol 193, 485-494 (2007).

Fig. S1 .
Fig. S1.Navigation arena design.(A) Side view.(B) Overhead view.The circular arena (150 cm diameter) was directly connected to a hive via an entrance located 25 cm from the arena's periphery (filled circle in B).Sugar water and pollen were provided in a conical feeder at the arena center.Neither the feeder nor hive-entrance were visible to bees in the arena.The arena was illuminated by an overhead light source that could either be highly polarized or depolarized.Experiments were video recorded from above.(C) Irradiance spectra of light available at the center of the arena (dashed line).Violet and blue curves: irradiance of the isolated UV and white LEDs from the overhead light source.Curves with colored area under the curve: Absorbance spectra of photoreceptor classes in the eyes of Bombus terrestris dalmatinus (from Skorupski et al. (54)).(D) Ratio of light transmitted through the overhead filter and a second crossed polarizer (perpendicular orientation/parallel orientation) when either the polarizer side (violet) or diffuser side (grey) faced towards the arena.

Fig. S2 .
Fig. S2.Photos of the navigation arena.Illuminated by (A) the overhead UV and white LEDs transmitted through the polarized filter.(B) Full hemispherical photo of the behavioral arena taken from the center of the arena oriented towards the hive at horizon with a fisheye lens.(C) Same photo as in (B) oriented 90° from the hive at horizon.(D) Full hemispherical photo of the behavioral arena taken from the center of the arena oriented towards zenith with a fisheye lens.(E) Same photo as in (D) overexposed.
, T. F. Döring, L. Chittka, Photoreceptor spectral sensitivity in island and mainland populations of the bumblebee, Bombus terrestris.J Comp Physiol A Neuroethol

Table S1 . Summary of orientation statistics for all experimental groups. Related to
Figures1CD, 2D, and 4B.Orientations were analyzed using Rayleigh Tests of Uniformity.Significance indicates that groups are oriented in a single direction.Only orientations of straight-line paths (see Methods) were used for analyses.Analyzed using doubled data.*When two groups were significantly oriented, their relative orientations were compared using a Watson Two-Sample Test of Homogeneity (last row).Significance indicates that groups are oriented differently from one another.

Table S2 . Summary of the generalized linear mixed models used in Figures 2E and 3E
. P < 0.05 indicate a significant effect of the predictor variable on the variable of interest.Incorporating the identity of the individual performing each homeward path did not significantly increase the explanatory power of any models (results of ANOVA analyses between models).

Table S3 . Summary of the maximum likelihood estimates of modal circular data structure for data used in Figure 4B.
The top best fit distribution models for both isolated displacements and displacements pooled together are the same.Therefore, an argument can be made for pooling both displacements.

Table S4 . Number of individuals that first oriented in the axis predicted from a long-term vector memory and that completed enough trials to meet the requirement of the experiment for all long-term vector memory experiments.
Related to Figures 2, 3, and 4.